Alarm switch for locks



Sept. 4, 1951 J. G. HOFLER I i 7 "2,566,335

ALARM swrrcn FOR LOCKS Filed Aug. 5, 1947 2 Sheets-Sheet 1 INVENTOR. Jamie Cary jYa/ler AGENTS.

P 1951 J. G. HOFLER 2,566,836

ALARM SWITCH FOR LOCKS Filed Aug. 5, 1947 2 Sheets-Sheet 2 I 'I I'I'I VENTOR. Jamie or Yo/ler Patented Sept. 4, 1951 UNITED STATES PATENT OFFICE ALARM SWITCH FOR LOCKS Jamie Georg Hofler, Copenhagen, Denmark Application August 5, 1947, Serial No. 766,233 In Denmark June 8, 1946 Section 1, Public Law 690, August 8, 1946 Patent expires June 8, 1966 12 Claims. (Cl. 20055) An object of the present invention is to provide an alarm device for association with a lock which is adjustable to signal each insertion of a key or other object into the lock, when in one condition, and to only signal or indicate the second insertion of a key into the look, when in another condition, so that with the device in thelast mentioned condition the door or other closure having the lock thereon may be locked from the outside without energizing the alarm and the alarm .will operat in response to a subsequent insertion of a key into the lock.

Another object is to provide an adjustable alarm device of the described character which is operated by the insertion of a key into the associated lock and is further adjustable to operate the alarm in one condition only during the residence of a key in the lock, and in another condition, to continue to operate the alarm even after the key has been removed from the look.

A further object is to provide an adjustable alarm device of the described character capable of adjustment to still another condition in which it is not responsive to the insertion of a key or other foreign object into the associated lock.

According to the present invention, the above objects are accomplished by providing an alarm device to be mounted on the inner side of a lock and comprising a longitudinally slidable pin spring urged to project outwardly into the key hole of th lock, 2. fixed contact and a movable contact engageable with the fixed contact to close an alarm circuit, and transmission mechanism actuated longitudinally by displacement of the slidable pin to control the engagement of the contacts, the transmission mechanism including longitudinally extending guide surfaces and being adjustable to selectively utilize the desired one of the guide surfaces in controlling engagement of the contacts. The transmission mechanism preferably is provided with a first guide surface shaped to close the contacts each time a key is inserted into the lock and to separate the contacts when the key is withdrawn; a second guide surface shaped to close the contacts each time a key is inserted and to retain the contacts in engagement when the key is withdrawn from the lock; 3, third guide surface shaped to hold the contacts apart the first time a key is inserted inthe associated lock and to provide for the engagement of the contacts only when a key is inserted a second time; and a fourth guide surface shaped to retain the contacts in spaced apart condition irresponsive to the repeated insertion of a key or other foreign article into the lock,

The above and other objects, features and advantages of the invention will appear in the following detailed description of a preferred embodiment of an alarm device according to the invention which is to be read with reference to the accompanying drawings, in which:

Fig. 1 is a side elevational view of a lock mounted on a door shown in section and provided with an alarm device according to the invention,

Fig. 2 a front view of a lock plate for mounting the alarm device,

Fig. 3 a longitudinal, horizontal section through the alarm device,

Fig. 4 a transverse, vertical section of the alarm device as ,it appears along the line IV-IV in Fig. 3,

Fig. 5 a side elevational view of an assembly included in the alarm device,

Fig. 6 an end elevational view of a guide member included in the alarm device,

Fig. 7 a longitudinal sectional view taken along the line VII-VII in Fig. 6, and

Fig. 8 a longitudinal sectional view taken along the line VIII-VIII in Fig. 6.

Fig. 9 is an isometric view of the guide member shown in Fig. 6.

Referring to the drawings in detail, and initially to Fig. 1 thereof, a look I is shown mounted in a door 3 and with the exception of the key hole 2 only the outlines of the lock are indicated. On the inner side of the door 3 a special lock plate 4 is placed in front of the key hole 2 for mounting the alarm deviceand is formed with a circular recess 5 having a threaded wall. The lock plate 4 has a central aperture 6, Fig. 2, aligned with the key hole 2. In the bottom of the recess 5 two mutually isolated semicircular contact strips 1 are mounted and separately connected with one of two terminals 8 which are so connected with an alarm system that an electrical connection between the two terminals will effect an alarm, for example by causing an electric bell to ring.

At one of the two places where the two contact strips 1 end opposite one another a resilient contact member 9 is secured in the lock plate 4 which tends to short-circuit the two contact strips but is prevented from doing so by means of a plug of insulating material, such as for example wood, extending through a hole in the lock plug II by suitable springs 15.

plate 4 and abutting against the look I. This contact member 9 serves to establish an alarm if a person should try to break oil the lock plate 4 from outside, the contact member 9 short-circuiting the contact strips 1 when the lock plate 4 gets loo'se because the wooden plug can then be pushed forwardly by the resilient contact member 9.

An alarm device enclosed in a casing ID is screwed into the lock plate 4. Fig. 1. v a v In one end of the cylindrical casing 10 an end plug H is secured having at. an end. projecting; from the casing and threaded as at l2 for engagement with the threaded wall of recess 5 in the plate 4, the adjacent end surface of the cas ing 10 limiting the screwing together of the two parts. tudinally slidable in the end plug H and are spring pressed outwardly through the face of The springs l5 are mounted in borings 1-6 in the end plug H and held in place by means of a washer l1 sefcu'red to the end plug.

When the device is screwed into the lock plate 4 the two contact plugs l3 and 1-4 will each engage one of the contact strips 1, the springs 15 securingthe establishment of the necessary ele tric contact;

i It'shoul d be noted that the lock plate having the contact strips 1 and the contact plugs 13 and I4 are only shown by way of example, and tha t the separable electric connections to the alarm device can be designed in many other suitable ways. a

The contact-plug 13- has such a length that its inner end extends only a rather short distance into the "casing the said-end forming a fixed contact of the device. the other contact plug i4 extendsa rather long distance into the casing anda'conta'ct arm 18 is pivoted and s-lidable on the inwardly extending portion of plug I4, Figs. 3 and 4. The free end 'of contact arm It forms the movable contact of the device andfcan be swung laterally into engagement with the contact plug [3 by the action of a spring I9. Figs. 4

and '5. Between the contact arm l8 and the inner headed end of the contact plug l4 a spring 26 is inserted, Fig. 3, securing the necessary electric connection between the contact plug l4 and the contact arm l8'.

A fixed stop 21 of substantially semi-cylindrical form; ,Fig; 5i, extends fixedly from the washer 1''! adjacent the fixed contact forming plug I3. Stop 2! is provided with a cutout 22 in itsupp'eredge adjacent the washer I! which of sufiicient depth so that the contact arm l8 may engage plug I3 when the arm is positioned "onplug M for" movement withinthe cutout Fig. 5. As seen in Fig. 5; the spring is extends at an angle relative to the plane of the swinging movement of contact arm 18 so that spring [9 not only urges the arm 28- to swing toward the fixed contact but. also to move axially along plug [4 away from washer and cutout 22'. The component of force exerted by spring 19' to effect this axial movement of contact arm i8 is greater than the force exerted by spring 26 on Thus, when contact arm i8 is lifted out of cutout 22 by mechanism hereinafter described, spring I}! moves the contact arm axially to ride on the upper edge of the stop 2|, which upper edge holds the contact arm away from. the fixed contact [3.

The end plug l I, Fig. 3, has a central aper- "tu'r'e 23 serving as'a guide for a pin 24 slidable screwed out of the guide member 25. The threaded end of the pin 24 has such a length that no portion of the thread will appear outside the guide member 26 whenthe pin has been screwed out of the said guide member so far as the end plate 29' allows; and it is thus possible to adjust the length of the portion of the pin 24 projecting outwardly of the device by screwing the pin more Two contact plugs l3 and [4V are longior less into the guide member 26.

Guide member 26 is formed with an annular rim intermediate its ends, and a spring 36 is disposed within casing In with one end thereof abutting against; and secured to, the rim. on guide member 2-6 and its other end secured to. a disc 3! abutting against an end plate or closure 32 at ,the. rear end of the casing. A shaft 33 is secured to disc 3| and extends. rotatably through a central opening 34 in end plate 32 for attachment to an adjusting hand wheel 35. The spring 36 acts to urge guide member 26 forwardly to project pin 24 into the key hole 2 and also provides a connection between hand wheel 35 and the guide member 26 so thatv the latter may be conveniently rotated within the casing; In the event that spring 30 is not strong enough. to transmit the rotation of wheel 35 to the guide member, suitable driving mechanism (not shown) permitting axial displacement of. the guide member may be interposed between the latter and the disc 3|, such as for example, a cylinder extending from disc 3| and having, longitudinal slots inits free end portion to receive radial pinscarriedby the guide member 26. p

In the most advanced position of the guide .mem-ber ZG-and the pin 24 the front end portion ofv the said guide member 26 projects into a boring 36 formed in the washer I! and endplug H. Theiront end. portion of the guide member 26 is further provided with longitudinally extending guide surfaces to be engaged by the contact arm I 8 and by means of which the pivoting of the contact arm l8 can be controlled. These guide surfaces are formed on the difierent portions of the circumference of the guide member so as to be selectively brought into position for engagement with the contact arm It by rotation of the guide member 26, the said rotation being effected by means of the hand wheel 35.

In the preferred embodiment of the invention illustrated by the drawings, guide member 26 is formed; with. four guide surfaces so that four different characteristics of operation are achievable depending, 'on which of the 'four surfaces is positioned for engagement with contact arm l 8 to actuate the latter when the guide member is moved axially by displacement of pin. 24-, as when a key or other object is inserted in key hole 2.

One o'fthese four guide surfacesis 'aguide surrace 31, Figs. '6' and '7, which is conical and so inclined relative to the axis of the guide member that the contact arm I8; engaging the rear portion of this conical or inclined guide surface 37 when the guide member 26 is in its foremost position, is swung away from the contact plug l3 but still remains inside the recess 22" of the stop 2|. When an Object, such. as for instance a key member 26 are pushed inwards, the conical or inclined form of the guide member permits the spring l9 to swing the contact arm I8 towards the contact plug I3 until contact is establihsed; the contact arm I8 being so designed and arranged as to establish contact with the contact plug I3 before engaging the pin 24. When the said contact is established the alarm circuit will be closed and continue thus until the object introduced into the key hole is again withdrawn so that the spring 36 may push the guide member 26 together with the pin 24 outwards with the effect that the inclined guide surface 3! lifts the contact arm l8 thereby disengaging the contacts. When the guide member is rotated to place guide surface 31 in operative position alarm is only effected during the period in which the foreign object is introduced into the key hole.

By rotating the guide member through 90 a second guide surface 38, 39 may be positioned for engagement with the contact arm l8. This guide surface has a cylindrical or plane surface 36 approximately parallel to the direction of axial motion of the guide member, and an end surface 39 approximately perpendicular to the surface 38. The surface 38 is so arranged on the guide member 26 that the contact arm I8 when abutting against the surface 38 is disengaged from the contact plug I3 but still remains inside the recess 22 of the stop 2|.

When the pin 24 is pushed in to displace guide member 26, the spring I9 will swing the contact arm I8 into contact with the contact plug I3 as soon as the forward edge of guide surface 38 has been moved beyond the path of swinging of the contact arm I8 as defined by cutout 22; so that the alarm circuit will be closed. When the object introduced into the key hole is withdrawn, however, in this case the end surface 39 will abut against the contact arm I8 which thereby stops the outward movement of the pin without being lifted so that the engagement of the contact arm I8 with the contact plug I3 is maintained even after the withdrawal of the object, and the alarm will be continued until it is manually interrupted.

By further rotating the guide member 26 a third guide surface 46-43 is brought into engagement with the contact arm I8. This guide surface is stepped and has a first step 40 toward the rear in the form of a surface approximately parallel to the direction of motion of the guide member 26 the said surface being either plane or cylindrical. This step has such a distance from the axis of the guide member 26 that the contact arm I8 when resting on step 46 will have been swung up above the stop 2| and by means of the spring I9 been carried in over the top edge of said stop 2|. The forward edge of step 40 is defined by a radial shoulder 4| which extends into a forward step defined by a surface 42 extending parallel to the direction of movement of member 26 and a radial or normal end surface 43. The surface 42 is substantially the same distance from the axis of rotation of member 26 as the surface 38, heretofore described, to produce the operating characteristics given below.

When guide member 26 is rotated to position guide surface 4043 for engagement with the contact arm I8 the latter will, as mentioned above, be initially lifted by surface 40 above the stop 2| some distance apart therefrom and moved by spring I9 over the top edge of the stop. When now the pin 24 is pushed in the surface 40 will move away from the contact arm I6 which in consequence thereof will swing down to rest against the top edge of stop 2| preventing the contact arm I8 from being swung into contact with the contact plug I3. When the key introduced into the key hole 2 is withdrawn and the guide member 26 is again moved outwardly by means of the spring 36, the shoulder 4| will abut against the contact arm I8 and carry the same along in this movement until it is swung down into the recess 22. thereof to rest against the surface 42 of the guide member 26. Next time the pin 24 is pushed in the end surface 43 will be displaced beyond the contact arm I8 which can then be swung by spring I9 into engagement with the contact plug I3 so that the alarm circuit is closed and maintained thus even when the object introduced into the key hole 2 is again withdrawn, the end surface 43 abutting against the contact arm and being incapable of lifting the latter.

It should be noted that the surface 42 may be inclined or conical in the manner of the aforementioned surface 31 so that after the pin 24 has been pushed in a first time, the alarm circuit will be closed only during the periods in which the pin 24 is subsequently held in the pushed-in position.

In the embodiment shown in the drawings the guide member also has a fourth guide surface 44, 45 (Fig. 8) consisting of a surface 44 approximately parallel to the direction of motion of the guide member and spaced from the axis of rotation of the latter a distance corresponding to the distance of surface 40 mentioned above from that axis, the said surface 44 ending in an inclined or conical surface 45. When the contact arm I8 engages the surface 44 it will assume a position above the top edge of stop 2| and be swung towards the same when the guide member 26 is pushed inwardly away from the contact arm. When, however, the guide member 26 is again moved outwardly later on the inclined or conical end surface 45 will engage the contact arm I8 and again lift the same into the position above the stop 2|, so that no alarm is established when this guide surface is in operative position.

When it is desired to interrupt the continuously closed alarm circuit established when guide surface 38, 39 or guide surface 40-43 is in operative position, the guide member 26 can be rotated to the position in which the guide surface 31 is effective, so that the spring 38 may urge the guide member forward to its normal position, and at the same time the guide surface 37 will swing the contact arm I8 away from the contact plug I3.

; Thereafter the guide member can again be rotated to place the desired guide surface in operative position.

As shown in Fig. 4 the contact arm I8 can also be provided with a lever 46 extending outwardly through a suitable slot in the casing I6, so that the contact arm I 8 can be manually swung away from the contact plug l3 by means of this arm 46.

While I have illustrated a specific embodiment of my invention, it is to be understood that various changes and modifications may be effected therein, such as, for example, by providing more than four guide surfaces on the guide member, Without departing from the scope or spirit of the invention and while utilizing the features thereof, which are intended to be defined by the appended claims.

I claim:

1. An alarm device adapted to be mounted on the inner side of a lock comprising a longitudinal ly slidable pin adapted to project outwardly into attests the key hole of said lock said pin being displaceable' inwardly upon insertion- (if a key into said any held; a pair of contacts adapted te engage one another to class the alarm circuit; a spring cdiis'tafitly urging said pin cutwardly; and adjustable transmission means actuated by dis placement of said pin and adapted to control the engagement of said contacts; said transmission means being adjustable into at least two positions, said transmission means in one of said positions effecting engagement of said contacts upon the first displacement of said pin, and in another of said positions maintaining said contacts out of engagement during the first displacement of said pin and effecting engagement of said contacts upon the second displacement of said pin;

2; An alarm device according to claim 1-,wherein one of said contacts is fixed, and the other of said contacts includes a movable contact arm spring urged into engagement with said fixed contact; and said transmission means includes aLrotatable guide member movable longitudinally with said pin; said guide member being formed with a plurality of longitudinally extending guide surfaces adapted to selectively engage said movable contact arm, each of said guide surfaces being so formed as to space said movable contact arm from said fixed contact when said pinis in the outermost position thereof.

3. An alarm device adapted to be mounted on the inner side of a lock comprising a longitudinally slidable pin adapted to project outwardly into the key hole of said lock, said pin being displaced inwardly upon insertion of a key into said key hole; a pair of contacts adapted to engage one another to close an alarm circuit; a spring constantly urging said pin outwardly; and adjustable transmission means actuated by displacement of said pin and adapted to control the engagement of said contacts; said; transmission means being adjustable into a pluralityof positions, said transmission means in one position thereof effecting engagement of said contacts when said pin is displaced and disengaging said contacts" when said pin is subsequently restored to the outermost position of said pin, said transmiss on means in a second position thereof effecting engagement of said contacts when said pin is displaced and continuing such engagement when the key effecting displacement of said pin is subsequently removed.

4. An alar'in' device according to claim 3, wherein one of said contacts is fixed, and the other of said contacts includes a movable contact arm spring urged into engagement with said fixed contact; and said transmission means includes a rotatable guide member movable axially with said pin, said guide member being formed with a plurality of axially extending guide surfaces adapted to selectively engage said movable cohtact arm, one of said guide surfaces being disposed substantially parallel to the direction of movement of said guide member and terminating abruptly at the outer end thereof and being engageablewith said contact arm in said second position of said transmission means, each of said guide surfaces when engaged with said contact arm being adapted to space the latter from said fixed contact when said pin is inthe outermost position thereof, and said one of said guide surfaces having a length such that said outer end thereof is clear of said contact arm when said pin is displaced to the innermost position thereof to thereby permit engagement of said contacts,

and whereby said abruptly terminated outer end of said one guide surface will bear longitudinally against said contact arm and prevent return of said pin to the outermost position.

5. An alarm device according to claim 4; where in said guide member is formed with another guide surface thereon inclined relative to the direction of axial motion of said guide member and forming an angle therewith of such degree that the contact arm will engage said fixed contact when said transmission means is disposed in said first position thereof and said pin is displaced inwardly to the innermost position thereof.

6. An alarm device according to claim 4, including a lever projecting radially from said transmission means and operatively connected to said contact arm, rocking of said lever effecting separation of said contact arm from said fixed contact.

7. An alarm device adapted to be mounted on the inner side of a lock comprising a longitudinally slidable pin adapted to project outwardly into the key hole of the lock, said pin being displaceable inwardly upon insertion of a key into the key hole; a fixed contact and a movable contact arm mounted for movement parallel to the direction of travel of said pin and for pivoting in a plane at right angles to said direction of travel; a fixed stop havin a notch formed therein; said contact arm in one longitudinal position being re ceived in said notch and being free to engage said fixed contact to close an alarm circuit, and in another longitudinal position thereof being arrested by an abutting surface of said stop and spaced from said fixed contact; means resiliently urging said contact arm to pivot towards said fixed contact and to move longitudinally to a position overlying said abutting surface of said stop; spring means constantly urging said pin outwardly; and adjustable transmission means for controlling the engagement of said contact arm and said fixed contact including a rotatable guide member movable longitudinally with said pm, said guide member being formed with a plurality of longitudinally extending guide surfaces adapted to selectively engage said movable contact arm, one of said guide surfaces being stepped and having a raised portion engageable with said contact arm and raising the latter above said notch to permit the movement of said contact arm to said spring urged longitudinal position, said raised portion of said stepped guide surface beingengaged with said contact arm when said pin is in the outermost position thereof; said stepped guide surface having a relatively depressed portion adapted when engaged with said contact arm to-raise the latter out of engagement with said fixed contact but to a position below said abutting surface of said stop, and steps formed between said raised and depressed portions and at the outenend of said depressed portion; whereby when said pin is initially displaced and restored to the outermost position thereof, said step between the raised and depressed portions of said guide surface will engage said contact arm and move the latter longitudinally into said notch;

and whereby a subsequent displacement of said pin will move said step at the outer end of said depressed portion under said contact arm to permit pivoting of the latter into engagement with saidfixed contact.

8; An alarm-device according to claim 7, wherein'said contact armis" spring urged by a coiled tension spring member extending obliquely in a direction towards said fixed contact and away from said notch in said stop.

9. An alarm device according to claim 7, wherein said notch formed in said stop engages the sides of said contact arm during pivoting of the latter towards said fixed contact to thereby serve as a side guide during such pivotal movement.

10. An alarm device according to claim '7, wherein said depressed portion of said guide surface is disposed substantially parallel to the direction of travel of said pin and terminates abruptly in said step on the outer end thereof, and the combined length of said raised and depressed portions is such that said depressed portion is moved past the contact arm when said pin is displaced to the innermost position thereof.

11. An alarm device according to claim 'I, wherein said depressed portion is inclined relative to the direction of movement of said pin so that the contact arm will engage the fixed contact when the outer end of said depressed portion is disposed under said contact arm.

12. An alarm device according to claim 7, wherein another of said guide surfaces is disposed substantially parallel to the direction of the axialmovement of said guide member, said last mentioned guide surface being spaced radial from the axis of said guide member a distance such that said contact arm when engaged therewith will be raised above said abutting surface of said stop, the outer end of said last mentioned guide surface terminating in an inclined end surface having an outer edge disposed closer to said axis of said guide member than the distance said abutting surface of said stop is spaced from said axis whereby said last mentioned guide surface will retain said contact arm in spaced relation to said fixed contact for all positions of said pin.

JAMIE GEORG HOFLER.

No references cited. 

